"So what percentage of our atmosphere is CO2 and what percentage of that amount is generated by human activity? Nitrogen is 78% of Earth's atmosphere, oxygen is 21% and carbon dioxide is 0.04% - four one-hundredths of a percent. Tiny amounts can still have huge consequences, but what percentage of 0.04% is natural and what is manmade? At the very least, 94% of atmospheric CO2 comes from natural sources, such as plant decay, decomposing carcasses, oceans and volcanoes. So just two one-thousandths of a percent of our atmosphere is manmade CO2. That means that all human-generated CO2 worldwide is the equivalent of a single can of cola out of a truckload of 50,000 cans." Lorne Gunter, writing in the Edmonton Sun, Canada.